To determine the incidence of hepatitis in prospectively followed open heart surgery patients receiving blood which has been pre-screened for donor transaminase (ALT) level. Blood units with elevated ALT will be discarded. Hepatitis incidence will be compared with that of identically followed patients in a recently completed study in which no attempt was made to exclude blood with elevated ALT. In that study blood units with elevated ALT were significantly more frequently associated with recipient hepatitis than units with normal ALT. Cases of hepatitis will be serologically assessed for virus etiology and patients will be carefully followed for the development of chronic hepatitis.